Hi all!

Problems with charging system were previously discussed in several threads...but I could not find a solution to my problem.

My 2004 civic's "battery light" starts blinking at morning cold start ups. Eventually, it shuts off after several minutes of driving ....15-20 minutes and the following "warm" start ups are trouble free....until next morning. Also, during these 15-20 minutes, the initial blink turns in a steady red light (when idle) and starts again blinking if the engine is revved.

This started about a week ago and I assume there is a problem with the charging system, but can't figure out what exactly.

Before the morning start, the battery shows 12.4 - 12.6 V and once started, it drops to 11.5 V. I draw the conclusion that the alternator does not charge the battery. Nevertheless, after "warming up" (battery light switches off), it charges the battery, as the voltage shows 14.4 - 14.7 V.

My guess is that something holds the alternator from charging the battery from the very beginning...but what?

If anyone has experienced a similar problem and managed to fix it, please help.

I would like to try myself, with your help, solving the issue...before going to dealers/mechanics.

Any input is valuable. Thanks

Are the alternator mounting bolts tight?
Is the belt tight? No loud screeech when you start it up?
EDIT: Connections tight?

If yes, then it sounds like a bad alternator.
How many miles on it/your car?

I have not touched alternator bolts....but I'll check them all tomorrow.
It has 195k km....about 120k miles

At all cost avoid parts stores cheap rebuilt, reman junk.

Do you have a automotive electrical shop in area ??

Sounds like worn brushes.

Today I've checked and cleaned battery connections and tried to get to the alternator, but failed...as I did not have a key to get to the second bolt of the power steering pump. Nevertheless, disconnected the + wire from alternator and the 4 pins connector. All seemed good, except the green regulator connector, which wouldn't "click" when trying to connect it back. I've pushed it as hard as I could and used some helping tools....but still not confident about the good connection, even if it won't disconnect when pulling it.

At a moment, after tightening all back, I've started the engine and the battery light did not come on....checked the voltage at the battery and it was charging with 14.5 V. I said myself that improper regulator connection caused all my troubles. Happy, I've attached the radio power cable to battery + and tried again....getting the light back on
No matter how much I tried....playing with that green connector around, I could not stop the light blinking.

Then I had to go to work and all was as before: blinking....then continuous light at the stops....blinking again when higher than 1000 rpm.....very fast blinks and then no more battery light. All further restarts (30-40 minutes) without the problem.

Also, when at the stop with battery light on and accelerating, the light starts blinking....and close to 4-5000 rpm is about to turn off, but I don't hold the rpms that high, so the light comes on at idle. I'll check tomorrow to see if the battery receives charge when revving that high.

Other than that, the voltage before first start was 12.49 at the battery and at alternator's +. Dropped at 11.5 when idle....the same at alternator's +.

Up to now, my feeling is that something electronic holds the alternator from sending charge to the battery and then decides that it's the time and starts working.

The belt is tight....that's how I feel it. It does not screek.

One more thing, when alternator kicks in, I feel a light wheeeeee. I assume it is coming from it. May it be from worn brushes?

What about the regulator? What's its job?

Thanks for thoughts.

are you saying the light only comes on when you connect your radio?

disconnect the radio and drive the car, is the problem still there?

im assuming this is an aftermarket stereo? how long have you had it installed?

Initially, I thought it might be related to attaching the stereo to the + terminal, but after removing it and disconnecting the battery terminals for a while then putting them back on, the alternator still would not send charge.
It is an aftermarket stereo and I do not know for how long it has been on the car....as I have the car for about a month only.

About 2 weeks ago I had my manual transmission rebuilt and clutch replaced.....coincidence or not, the battery light issue started to come after this. I am thinking it could not be a an effect of the repairs I have done....but who knows?! Is anything that you may suggest to check?

The main battery ground cable attaches to the trans. Maybe you should check that?


Regulator is inside the alternator. It regulates charging voltage.

the alternator controls the light on the dash. It's not the only thing that can control the light though.

The alternator, when it begins to generate electricity, becomes a noticeable load on the engine. You may be able to feel it. You may be able to hear (whine or howl) when it is charging at a high rate too.

It's been a mistery so far....

Yesterday I've managed to pull out the alternator from the car. I wanted to inspect the brushes. Unfortunately, the cover was so tightly stick to the body that I could not open it. Then I went with it to Honda dealer to see if they could test it. Their answer was- they can't test it out of the car and recommended to put it back and come with the car, so that they could "test" it. When asking what kind of test will they perform, the guy from the service replied that "using the voltmeter....to see if alternator produces voltage". I've explained that this I ve already done and explained alternator's behaviour. Then he said that it's most likely another problem than the alternator. He would suspect a wiring problem....

And this is how I've put my alt back on the car....'cause I needed the car. After putting all back...tightening all bolts, connections...checking the "-" cable that goes to transmission, started the engine and the light was off. I said, well, it probably wanted to be baby-ed.

After 2 hours started the car to go to work and the light was back on
Drove it around 15 min....revved it once - twice to 6000 rpm and the light went off. Stopped the car.....restarted after 15 min and the light on again. Revved one shot to 6000 rpm and the light switched off......after that no issues, during over 40 stops-restarts in 12 hours timeframe.

What would be your suggestions?

Thanks all

That's correct, we have no way to bench test an alternator.

Try your local parts stores or a rebuilder.
Wow. That's really dumbed down....Or maybe the person you spoke to has no real clue what goes on behind the mystery door. Many advisors (they are only salespeople) really don't know a dang thing about cars.

Hint: Witchcraft.

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Check: When the light is on solid: Unplug that 4 wire plug from the alternator and see if that kills the light. If so, then the alternator is turning the light on.

If the light stays on while the alt is unplugged, then something else is controlling the light.

I did that several days ago when trying to see if improper connection of the 4 wire plug could trigger the problem. I've been pressing it, unplugging....all these with engine running. I've noticed that the light would turn off when the 4 wires were unplugged.

I would say that the light sends correct information, in the sense that it lights up when alternator is not doing the job.

Yesterday I've once again confirmed the "practice" that switches the light off and subsequently, engages alternator to work - revving to 6000 rpms. I am thinking about several things now: the belt, brushes, regulator.
Could a worn belt trigger this? It really should be changed...noticed that when took it off 2 days ago.
What about the brushes? I am bit reserved, as I am thinking if brushes are bad, they would behave as bad all the time....I might be wrong, please correct me if so.
And regulator itself....maybe some internal circuits are damaged....

What would you think related to 6000 rpm "cure" ?

as long as the belt is tight enough, a "worn" belt would make no difference, i think you are just trying to stretch things hoping for a simple solution,

at this point if it was my car i would just replace the alt and see what happens, but thats just my 2 cent opinion

Replace the alternator.

Or maybe take it to a reputable rebuilder.

Again